\begin{calstable}
\colwidths{{1cm}{7cm}{1cm}}
\brow \cell{x} \cell{x} \cell{x} \erow
\brow \cell{x} \cell{
\columnsep=0cm\relax
% Force multicols to regard our \leftskip
% by pretending that we are a list.
\@totalleftmargin=\cals@paddingL\relax
\begin{multicols}{2}

\begin{calstable}
\alignR
\colwidths{{1.5cm}{1.5cm}}
\thead{\brow \cell{$n$}\cell{$n^2$} \erow}
\tfoot{\brow \cell{$n$}\cell{$n^2$} \erow}
\brow \cell{2}  \cell{4}   \erow
\brow \cell{3}  \cell{9}   \erow
\brow \cell{4}  \cell{16}  \erow
\brow \cell{5}  \cell{25}  \erow
\brow \cell{6}  \cell{36}  \erow
\tbreak{\break }
\brow \cell{7}  \cell{49}  \erow
\brow \cell{8}  \cell{64}  \erow
\brow \cell{9}  \cell{81}  \erow
\brow \cell{10} \cell{100} \erow
\brow \cell{11} \cell{121} \erow
\end{calstable}

\end{multicols}
} \cell{x} \erow
\brow \cell{x} \cell{x} \cell{x} \erow
\end{calstable}